1. Field of the Invention
This invention relates generally to optical transmission systems. More particularly this invention relates to devices that switch light signals from input ports to selected output ports connected to fiber optic transmission cables.
2. Description of Related Art
Optical switches, particularly 2×2 optical switches, are known in the art. Examples of such switches are the SW2×2-9N12-16 manufactured by Sercalo Microtechnology, Ltd., Principality of Liechtenstein and the F04635 manufactured by Poly-Scientific Fiber Optic Products of Northrop Grumman Corporation, Blacksburg Va. Each of these optical switches employ optical micro electromechanical systems to adjust mirrors to steer light signals from input ports to output ports. Generally, the input ports and the output ports are placed on opposing sides of the packaging of the optical switch.
In many of the existing optical switches, six or more mirrors are used to steer the light signals from the input ports to the output ports. The additional mirrors add to the complexity of the optical path and increase the insertion loss and light dispersion of the switch. Further, having the connections for the input and output ports on opposing sides of the switch complicates the packaging and system structure of an optical network.
U.S. Pat. No. 6,002,818 (Fatehi, et al.) describes a free-space optical signal switch. The optical signal switch employs a rotating prism for transmitter beam steering for controlling to which receiver an optical signal from a transmitter is directed.
U.S. Pat. No. 6,415,067 (Copner, et al.) reveals a four port optical switch. The switch consists of two GRIN lenses. Each of the two GRIN lenses has two of the optical ports placed to receive light placed at their outer end face. A movable optical element in the form of a light transmissive wedge having a reflective surface is selectively moved into the path between the two GRIN lenses to direct a light signal from the first GRIN lenses to the second GRIN lens. The wedges have a reflective surface to direct light signals from one port of the two GRIN lenses to the adjacent port of the adjacent port on the same GRIN lens. A second wedge is employed to direct the light signal between different ports of the two GRIN lenses.
U.S. Pat. No. 6,005,998 (Lee) teaches a scalable, non-blocking fiber optic matrix switch. The matrix switch has two arrays of light beam collimators arranged to face one another in free space, and a number of optical fibers coupled to each of the arrays. Each collimator has a tubular body with a fiber receiving part at one end, and a lens mounting part at an opposite end of the body. A lens fixed in the mounting part produces a collimated light beam from light emitted from an end of an optical fiber inserted in the fiber receiving part. First and second motor assemblies with corresponding positioning elements displace the collimator body so that its light beam is steered to a desired position along “X” and “Y” axes in response to operation of the motor assemblies. A signal carried on a fiber entering a first collimator in one array can be switched into a fiber of a second collimator in the opposite array, by displacing the collimators so as to direct the beam of the first collimator to align with a lens axis of the second.
U.S. Pat. No. 6,259,835 (Jing) illustrates a mechanically actuated optical switch including stationary and movable optical reflectors. The movable reflectors are transferred between their on and off positions to switch an input optical signal to any one of multiple output optical fibers selected for transmitting the optical signal. The moveable reflectors are connected to an arm that is attached to a relay that causes the arm to selectively move. When the arm moves, the reflectors are placed in the path of the optical signal to transfer the signal to the output optical fibers.
U.S. Pat. No. 6,285,022 (Bhalla) demonstrates a front accessible optical beam switch. The optical beam switch is designed for improved serviceability by mounting two fiber optic beam deflection arrays to face the front of a rack assembly. Inside the optical beam switch, a mirror is located behind each of the two fiber optic beam deflection arrays and used to reflect the light beams between the two fiber optic beam deflection arrays. A controller adjusts the angle of the mirror such that the two fiber optic beam deflection arrays.
U.S. Pat. No. 6,385,364 (Abushagur) reveals an optical switch that guides data transmitting light beams along free space switching paths from one or more input optical fibers to one or more output optical fibers. The optical switch includes a microchip base member, diffractive, refractive or reflective optical elements positioned on carrier panels, and actuators for moving the carrier panels. The optical elements are able to be position by the actuators to guide light beams emitted by the input optical fibers in free space to the receiving output optical fibers. The actuators may be linear and/or rotary. Switching of light beams can be from one input port to one or many output ports, and vice versa, to form a free space optical cross-connect switch and router.
U.S. Pat. No. 6,396,976 (Little, et al.) describes a two dimensional optical switch. An array of micromachined mirrors are arranged on a first substrate at the intersections of input and output optical paths and oriented at approximately forty-five degrees to the paths. An array of split-electrodes is arranged on a second substrate above the respective mirrors. Each split electrode includes a first electrode configured to apply an electrostatic force that rotates the mirror approximately ninety degrees into one of the input optical paths to deflect the optical signal along one of the output optical paths, and a second electrode configured to apply an electrostatic force that maintains the mirror position.
U.S. Pat. No. 5,000,534 (Watanabe, et al.) shows an optical switch that includes at least one optical fiber exit terminal disposed in a plane, multiple optical fiber entrance terminals disposed in the plane, and a movable reflector disposed in the plane and angularly movable about a point in the plane for reflecting and/or refracting a light ray from the optical fiber exit terminal selectively into one of the optical fiber entrance terminals for thereby optically coupling the optical fiber exit terminal and to one of optical fiber entrance terminals.